The present invention is directed to a process for preparing dianthranilate compounds. More specifically, the present invention is directed to a process for preparing dianthranilate compounds containing relatively large hydrocarbon moieties, and to processes for preparing diazopyridone colorants with these dianthranilate compounds. One embodiment of the present invention is directed to a process for preparing dianthranilate compounds which comprises (a) admixing (1) a diol of the formula R1(OH)2, wherein R1 is an alkylene group having at least about 20 carbon atoms, and wherein the xe2x80x94OH groups are primary or secondary, (2) isatoic anhydride, present in an amount of at least about 2 moles of isatoic anhydride per every one mole of diol, (3) a catalyst which is 1,4-diazabicyclo[2.2.2]octane, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylethylene diamine, or a mixture thereof, said catalyst being present in an amount of at least about 0.2 mole of catalyst per every one mole of diol, and (4) a solvent; and (b) heating the mixture thus formed to form a dianthranilate compound of the formula 
Another embodiment of the present invention is directed to a process for preparing a diazopyridone colorant which comprises (I) preparing a dianthranilate compound by (a) admixing (1) a diol of the formula R1(OH)2,wherein R1 is an alkylene group having at least about 20 carbon atoms, and wherein the xe2x80x94OH groups are primary or secondary, (2) isatoic anhydride, present in an amount of at least about 2 moles of isatoic anhydride per every one mole of diol, (3) a catalyst which is 1,4-diazabicyclo[2.2.2]octane, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylethylene diamine, or a mixture thereof, said catalyst being present in an amount of at least about 0.2 mole of catalyst per every one mole of dial, and (4) a solvent; and (b) heating the mixture thus formed to form a dianthranilate compound of the formula 
(II) reacting the dianthranilate compound with nitrosylsulfuric acid to form a diazonium salt of the formula 
and (III) reacting the diazonium salt with a pyridone compound of the formula 
wherein R2 is (i) an alkyl group, (ii) an aryl group, (iii) an arylalkyl group, (iv) an alkylaryl group, (v) an alkoxy group, (vi) an aryloxy group, (vii) an arylalkyloxy group, (viii) an alkylaryloxy group, (ix) a polyalkyleneoxy group, (x) a polyaryleneoxy group, (xi) a polyarylalkyleneoxy group, (xii) a polyalkylaryleneoxy group, (xiii) a heterocyclic group, (xiv) a silyl group, (xv) a siloxane group, (xvi) a polysilylene group, (xvii) a polysiloxane group, or (xviii) a group of the formula 
wherein r and s are each, independently of the other, integers representing a number of repeat xe2x80x94CH2xe2x80x94 groups, and R3 is (i) an alkyl group, (ii) an aryl group, (iii) an arylalkyl group, or (iv) an alkylaryl group, to form a diazopyridone compound of the formula 
Methods for the preparation of simple anthranilate esters with isatoic anhydride and simple alcohols are known. These methods, however, when used to attempt to prepare anthranilate compounds from diols of relatively large hydrocarbons, exhibit disadvantages such as low yield and the production of undesirable intermediate products and byproducts. Moreover, known syntheses of dianthranilates have the added complication of entailing two consecutive additions of an intermediate, isatoic anhydride, to a diol, which can lead to contamination by a monoanthranilate mono alcohol if the reaction is not forced to completion. This monoanthranilate can be difficult to remove from the dianthranilate. Dianthranilates containing relatively large hydrocarbon moieties can be used to prepare specific diazopyridone colorants.
U.S. Pat. No. 3,929,863 (Blahak et al.) and German Patent Publication DE 2 040 644, the disclosures of each of which are totally incorporated herein by reference, disclose aromatic diamines having the general formula 
wherein n is an integer of from 2 to 8, X is sulfur or oxygen, and R is an n-valent hydrocarbon radical which may be interrupted by O or S atoms and which is obtained by removing OH or SH groups from a polyol or polythiol having a molecular weight of less than 600 which are prepared by reacting a compound having the formula (HX)nR where X, n, and R as defined above with about n-equivalents of an isatoic acid anhydride in the presence of a strong base. The aromatic diamines of the invention are particularly useful as the active hydrogen containing component for reaction with polyisocyanates in the preparation of synthetic resins by the isocyanate-polyaddition process.
German Patent Publication DE 2 902 740 and European Patent Publication EP 0 013 956, the disclosures of each of which are totally incorporated herein by reference, disclose a process for the preparation of bis-(aminobenzoic acid)-alkanediol diester by esterification of alkanediols, except those in which hydroxy groups are in 1.4 or 2.5-positions, which nitrobenzoic acids and subsequent catalytic reduction of the bis-(nitrobenzoic acid)-alkanediol diester compound in a polar organic solvent, this solvent being partly or homogeneously miscible with water in all proportions, characterized by that the esterification is carried out in the presence of an aromatic sulfonic acid as a catalyst and in the absence of a solvent and at a temperature between 150 and 175xc2x0 C.
xe2x80x9cPolyamines Containing Ester Groups as Structural Components in Polyurethane Chemistry, J. Blahak et al., Angew. Makromol. Chem. (1972), Vol. 26, pp. 29 to 45, the disclosure of which is totally incorporated herein by reference, discloses aromatic diamines containing ester groups, such as 4-chloro-3,5-diaminobenzoates and aminophenyl aminobenzoates, which were prepared and used as noncarcinogenic and nontoxic chain extenders for polyurethane elastomers, giving processing and mechanical properties similar to those obtained with 3,3xe2x80x2-dichloro-4,4xe2x80x2-diaminodiphenylmethane. Anthranilates of both high and low molecular weight polyols were also used, but were much less reactive than compounds with amino groups in the meta or para position.
xe2x80x9cThe Chemistry of Isatoic Anhydride,xe2x80x9d G. M. Coppola, Synthesis, p. 505 (1980), the disclosure of which is totally incorporated herein by reference, discloses various reactions to synthesize isatoic anhydride and reactions of isatoic anhydride with various classes of compounds, including alcohols.
xe2x80x9cIsatoic Anhydride. IV. Reactions with Various Nucleophiles,xe2x80x9d R. P. Staiger et al., J. Org. Chem., Vol. 24, p. 1214 (1959), the disclosure of which is totally incorporated herein by reference, discloses reactions of isatoic anhydride with alcohols, mercaptans, and compounds with active methylene groups forming substituted esters, thio esters, carbamates, and substituted quinolines. A mechanism for the alternate cleavage of the anhydride ring is elucidated.
European Patent Publication 1 125 990 and PCT Patent Publication WO 01/09256, the disclosures of each of which are totally incorporated herein by reference, discloses an aqueous ink for ink jet recording which contains at least a water-insoluble coloring matter, water, and a resin as main components and which takes the form of an emulsion, which is characterized by containing at least one yellow hue coloring matter selected from the group consisting of a quinophthalone compound represented by the formula (1) 
wherein each of R1 to R3 independently represents a hydrogen atom, an unsubstituted or substituted alkyl group, xe2x80x94CONR4R5, or xe2x80x94COOR6 (in which each of R4 to R6 independently represents a hydrogen atom, an unsubstituted or substituted alkyl group, or an unsubstituted or substituted aryl group) and all of R1 to R3 are not a hydrogen atom at the same time, and a pyridone azo compound represented by the formula (2) 
wherein each of R7 to R11 independently represents a hydrogen atom, a halogen atom, an unsubstituted or substituted alkyl group, an aralkyl group, an unsubstituted or substituted alkoxy group, an unsubstituted or substituted aryl group, an unsubstituted or substituted aryloxy group, a hydroxyl group, xe2x80x94NR14R15 (in which R14 and R15 independently represent a hydrogen atom, an unsubstituted or substituted alkyl group, or an aralkyl group), xe2x80x94COX1 (in which X1 represents an unsubstituted or substituted alkoxy group, an unsubstituted or substituted aryloxy group, or xe2x80x94NR16R17 (in which each of R16 and R17 independently represent a hydrogen atom, an unsubstituted or substituted alkyl group, an aralkyl group, or an unsubstituted or substituted aryl group)), xe2x80x94COO(CH2)nxe2x80x94COX2, xe2x80x94OCOX3, or xe2x80x94NHCOX4 (in which each of X2 to X4 independently represents an unsubstituted or substituted alkyl group, an aralkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted alkoxy group, or an unsubstituted or substituted aryloxy group, and n is an integer of 1 to 3), R12 represents an unsubstituted or substituted alkyl group, and R13 represents"" an unsubstituted or substituted alkyl group, an aralkyl group, or an unsubstituted or substituted aryl group. The ink is for ink jet recording having excellent light resistance and storage stability, and enables formation of a high quality image without blotting, and the obtained recording image is excellent in water resistance.
PCT Patent Publication WO 01/21714, the disclosure of which is totally incorporated herein by reference, discloses compositions comprising a solvent and at least one compound of the 
in which R1 represents H, an optionally substituted C1-8 carbyl derived group, or a group of the formula 
where C is from 2 to 6, R3 represents optionally substituted C1-8 carbyl derived group, R4 and R5 independently represent an optional substituent, R2 represents an optionally substituted C1-8 carbyl derived group, X Y, and Z independently represent H or an optional substituent, M represents H or a cation, and m and n independently represent 0,1, or 2. Also disclosed are compounds of the above formula providing that at least one of R1, R2, X, Y, or Z comprises a group of formula SO3M or PO3M2. These compositions and compounds are useful as the colorants to prepare color filters for displays.
U.S. Pat. No. 4,247,456 (von Brachel et al.), the disclosure of which is totally incorporated herein by reference, discloses water-insoluble monoazo dyes of the formula 
wherein R is the residue of a benzene, naphthalene, diphenyl, diphenylmethane, or heterocyclic diazo compound which is free from water solubilizing groups, produced by reacting a diazotized amine of the benzene, naphthalene, diphenyl, diphenylmethane, or heterocyclic series which is free from water solubilizing groups with the appropriate 6-hydroxy-2-pyridone and the utility thereof for the dyeing and printing of synthetic fabric materials to yellow to red shades having excellent fastness to light and sublimation.
U.S. Pat. No. 3,957,749 (von Brachel et al.), the disclosure of which is totally incorporated herein by reference, discloses water-insoluble monoazo dyes of the formula 
produced by reacting a diazotized amine of the benzene, naphthalene, diphenyl, diphenylmethane, or heterocyclic series which is free from water solubilizing groups with the appropriate 6-hydroxy-2-pyridone and the utility thereof for the dyeing and printing of synthetic fabric materials to yellow to red shades having excellent fastness to light and sublimation.
Japanese Patent Publication JP 05331382, the disclosure of which is totally incorporated herein by reference, discloses a specific pyridone azo pigment which is bright yellow and highly soluble in a solvent, absorbs light of long wavelength, and is useful for a thermal transfer sheet. The pyridone azo pigment is represented by the formula 
wherein R is H, alkyl, substituted alkyl, cycloalkyl, aryl, or optionally substituted phenyl, and ring A is a benzene ring optionally having a nonionic group. The pigment is prepared by diazotizing an aniline compound and coupling the resulting diazo compound with a pyridone compound. Having a good solubility in an organic solvent and a good dispersibility in water, the pigment facilitates the preparation of an ink containing a high concentration of the pigment homogeneously dissolved or dispersed. The prepared ink enables the preparation of a thermal transfer sheet coated with the ink uniformly in a high density.
British Patent 1,559,001 (Harvey et al.), the disclosure of which is totally incorporated herein by reference, discloses a hydrophilic textile material colored with a dyestuff of the formula 
wherein D is the residue of a diazo or tetrazo component; R1 is a hydrogen atom or an alkyl, chloro, acetamido, benzamido, carbamoyl, or an N-substituted carbamyl, for example xe2x80x94CONHBr, group or, preferably, a cyano group; R2 is an alkyl group, especially methyl, optionally substituted with a chlorine atom, a phenyl group, optionally substituted with an alkyl or alkoxy group, or a carboxylic acid or carboxylic acid ester group; or R1 and R2 together with the carbon atoms in the 3- or 4-position of the pyridone ring may form an alicyclic or aromatic ring system so that, for example, R1 and R2 together may be a tri- or tetra-methylene group forming with the pyridone of penteno [c] or hexeno [c] pyrid-2-one, or R1 and R2 may form together with the adjacent carbon atoms of the pyridone ring a benzene ring giving a benz [c] pyrid-2one; R3 is an aryl group carrying one or more substituents selected from xe2x80x94NO, xe2x80x94SO2R1, xe2x80x94COR1, xe2x80x94COOR1, xe2x80x94CF, or xe2x80x94CN, wherein R1 is an optionally substituted alkyl or aryl group; and n is an integer which may be 1 or 2.
German Patent Publication DE 19646430, the disclosure of which is totally incorporated herein by reference, discloses dye mixtures comprising at least two structurally different dyes, each corresponding to formula 
wherein R1 is C1-C4 alkyl; R2 is the (CH2)nOxe2x80x94R5 radical; R5 is, independently of R1, C1-C4 alkyl or phenyl (which is unsubstituted or substituted by C1-C4 alkyl, C1-C4 alkoxy, hydroxy, or halogen); and n is 2 or 3, which dye mixtures are suitable for dyeing or printing textile fibre materials (e.g. polyester materials), giving dyeings having good around fastness properties.
German Patent Publication DE 19646429, the disclosure of which is totally incorporated herein by reference, discloses dye mixtures comprising at least two structurally different dyes, each of which has the formula 
in which R1 is C1-C4 alkyl and R2 is isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl; or C1-C3 alkyl which is substituted by phenyl or phenoxy; or R1 is phenyl (which is unsubstituted or substituted by C1-C4 alkyl, C1-C4 alkoxy, hydroxyl, or halogen), C1-C4 alkoxy-C1C3 alkylene, phenoxy-C1-C3 alkylene, or C1-C3 alkyl which is substituted by phenyl (which is unsubstituted or substituted by C1-C4 alkyl, C1-C4 alkoxy, hydroxyl, or halogen) and R2 is C1-C10 alkyl (which is unsubstituted or substituted by hydroxyl, OCOR3, or phenoxy, where the phenyl ring in phenoxy is unsubstituted or substituted by C1-C4 alkyl, C1-C4 alkoxy, hydroxyl, or halogen) and the alkyl chain in C1-C4 alkyl from C2 can be interrupted by one or more oxygen atoms; phenyl (which is unsubstituted or substituted by C1-C4 alkyl, C1-C4 alkoxy, hydroxyl, or halogen); or C5-C7 cycloalkyl; and R3 is C1-C4 alkyl, are suitable for dyeing or printing textile fibre materials (e.g. polyester materials) and give dyeings with good allround properties.
German Patent Publication DE 19647869, the disclosure of which is totally incorporated herein by reference, discloses a dye mixture containing at least 2 dyes with different structures, each of formula 
where R1 is a 1-4C alkyl; and R2 is a linear 1-3C alkyl. Also claimed is hydrophobic fibre material, preferably polyester textile material, dyed or printed with the mixture.
PCT Patent Publication WO 99/43754, the disclosure of which is totally incorporated herein by reference, discloses compounds of the formula 
and salts and toutomers thereof, wherein: R1 and R2 each independently is H, optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyl; each W and each X independently is xe2x80x94COOH, xe2x80x94SO3H, xe2x80x94PO3H2, or alkyl substituted by one or more groups selected from xe2x80x94COOH, xe2x80x94SO3H, and xe2x80x94PO3H2; each Y and each Z independently is a substituent other than those defined for W and X; a and d each independently is 1 to 5; b and c each independently is 0 to 4; (a+b) has a value of 5 or less; and (c+d) has a value of 5 or less. Also claimed are inks containing a compound of this formula, an ink jet printing process using the inks, substrates printed with the inks, and ink jet printer cartridges containing the inks.
U.S. Pat. No. 5,929,218 (Lee et al.), the disclosure of which is totally incorporated herein by reference, discloses pyridone-based yellow monoazo dyes used in thermal transfer having following formula which have good stability and hue 
wherein R1 is hydrogen atom; unsubstituted or substituted alkyl group of from 1 to 8 carbon atoms with alkoxy or aryl; or unsubstituted or substituted aryl group with alkoxy or halogen, and X is hydrogen atom; alkyl group of from 1 to 4 carbon atoms; alkoxy group; or halogen; R2 is selected from the following groups; 
wherein R3 and R4 are independently selected from groups consisting hydrogen, substituted or unsubstituted alkyl group of from 1 to 4 carbon atoms, halogen, alkyl carboxylate, and carbonyl group: R3-R4 is noncyclization with R3 and R4 and selected respectively from the above substituents (R3 and R4) or saturated or unsaturated cycloalkyl of from 3 to 6 carbon atoms, Z is nitro, halogen, alkyl group of from 1 to 4 carbon atoms, alkoxy, sulfonyl, carbonyl, carboxyamide, sulfonamino, cyano, hydroxy, or hydrogen atom.
European Patent Publication EP 0 706 679 B1, U.S. Pat. No. 5,853,929 (Campbell), and PCT Patent Publication WO 95/00885, the disclosures of each of which are totally incorporated herein by reference, disclose colored cyan toner for electroreprography and laser printing based on Solvent Blue 70, and a trichomatic set of coloured toners based on Solvent Blue 70, benzodifuranone red dyes, and azo pyridone yellow dyes of the formula 
wherein X is halogen, nitro, or a group xe2x80x94COOR5, R9 is C1-12 alkyl, R5 is C1-8 alkyl or a group of formula xe2x80x94(C1-3-alkylene)-(CO)qxe2x80x94Z wherein q is 0 or 1 and Z is xe2x80x94OR6 or xe2x80x94NR6R7 when q=1 or Z is xe2x80x94OR8 when q=0, R6 is selected from optionally substituted C1-8 alkyl, optionally substituted C1-8 alkoxy-C1-8 alkyl, and a second group represented by R5 in which R6 is optionally substituted C1-8 alkyl or optionally substituted C1-8 alkoxy-C1-8 alkyl, R7 is selected from H and optionally substituted C1-8 alkyl, and R8 is selected from optionally substituted C1-8 alkyl, optionally substituted C1-8 alkoxy-C1-8 alkyl, optionally substituted C1-8 alkyl sulfonyl or carbonyl, and optionally substituted phenyl sulfonyl or carbamoyl.
European Patent Publication EP 0 247 737, the disclosure of which is totally incorporated herein by reference, discloses a thermal transfer printing sheet suitable for use in a thermal transfer printing process, especially for the conversion of a digital image into a visible print, comprising a substrate having a coating comprising a dye of the formula 
wherein Ring A is unsubstituted or carries, in the 2- or 4-position with respect to the azo link, at least one group selected from xe2x80x94CX3, X1, CN, NO2, xe2x80x94OCO.Y, xe2x80x94CO.Y, xe2x80x94CO.H, xe2x80x94OS2.Y, and xe2x80x94SOO2. Y, provided that A is substituted when Z is CH3 and R is C2-4-alkyl; X and X1 are each independently halogen; Y is selected from R1, xe2x80x94OR1, SR1, and xe2x80x94NR1R2; R1 is selected from C1-12-alkyl, C1-12-alkyl interrupted by one or two groups selected from xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, O.COxe2x80x94, and xe2x80x94CO.Oxe2x80x94, C3-7-cycloalkyl, mono- or bi-cyclic aryl, and C1-3-alkylene attached to an adjacent carbon atom on Ring A; R2 is selected from H, C1-12-alkyl, C3-7-cycloalkyl, and mono-or bi-cyclic aryl; Z is C1-12-alkyl or phenyl; and R is selected from C2-12-alkyl unbranched in the alpha-position, C2-12-alkyl unbranched in alpha-position and interrupted by one or two groups selected from xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, O.COxe2x80x94, and xe2x80x94CO.Oxe2x80x94, phenyl, C1-4-alkylphenyl, biphenyl, and biphenyl interrupted by a group selected from xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, O.COxe2x80x94, and xe2x80x94CO.Oxe2x80x94, each of which is free from hydrogen atoms capable of intermolecular hydrogen bonding.
U.S. Pat. No. 5,041,413 (Evans et al.), the disclosure of which is totally incorporated herein by reference, discloses a yellow dye-donor element for thermal dye transfer comprises a support having thereon a dye layer comprising a mixture of yellow dyes dispersed in a polymeric binder, at least one of the yellow dyes having the formula 
wherein: each R1 independently represents a substituted or unsubstituted alkyl group of from 1 to about 10 carbon atoms, a cycloalkyl group of from about 5 to about 7 carbon atoms; a substituted or unsubstituted allyl group; an aryl group of from about 6 to about 10 carbon atoms; a hetaryl group of from 5 to 10 atoms; acyl; arylsulfonyl; aminocarbonyl; aminosulfonyl; fluorosulfonyl; halogen; nitro; alkylthio; or arylthio; or any two adjacent R1""s together represent the atoms necessary to form a 5- or 6-membered fused ring; n represents an integer from 0-4; R2 represents hydrogen; a substituted or unsubstituted alkyl, cycloalkyl, allyl, aryl or hetaryl group as described above for R1; cyano; acyl; alkylsulfonyl; arylsulfonyl; or alkoxycarbonyl; Z represents cyano; alkoxycarbonyl; acyl; nitro; arylsulfonyl or alkylsulfonyl; Y represents hydrogen; a substituted or unsubstituted alkyl, cycloalkyl, allyl, aryl or hetaryl group as described above for R1; amino; alkylamino; arylamino; acylamino; or sulfonylamino; and at least one of the other of the dyes having the formula 
wherein R3 represents the same groups as R1 above; R4 and R5 each independently represents hydrogen, R3; cyano; acyloxy; alkoxy of 1 to about 6 carbon atoms; halogen; or alkoxycarbonyl; or any two of R3, R4 and R5 together represent the atoms necessary to complete a 5- to 7-membered ring; R6 represents the same groups as R3; G represents a substituted or unsubstituted alkyl, cycloalkyl or allyl group as described above for R3, NR7R8 or OR9; R7 and R8 each independently represents hydrogen, acyl or R3, with the proviso that R7 and R8 cannot both be hydrogen at the same time; or R7 and R8 together represent the atoms necessary to complete a 5- to 7-membered ring; R9 represents the same groups as R3; X represents C(R10)(R11), S, O or NR10; R10 and R11 each independently represents the same groups as R3; or R10 and R11 together represent the atoms necessary to complete a 5- to 7-membered ring; and J represents the atoms necessary to complete a 5- or 6-membered ring which may be fused to another ring system.
U.S. Pat. No. 4,359,418 (Lienhard et al.), the disclosure of which is totally incorporated herein by reference, discloses azo dyestuff sulfonic acid salts of the formula 
wherein A represents a carbocyclic or heterocyclic aromatic radical, B represents an aliphatic, cycloaliphatic or araliphatic amine, X represents a hydrogen atom or a substituted or unsubstituted alkyl group, a cycloalkyl, aralkyl or aryl group, Y represents a hydrogen or halogen atom, a nitro, cyano, acyl, sulfonic acid, arylsulfonyl, alkoxycarbonyl group or a substituted or unsubstituted alkyl, sulfamoyl or carbamoyl group, Z represents a substituted or unsubstituted alkyl group or an aryl radical, m and n are 1 or 2; said dyestuffs salts having good solubility in organic solvents and functioning to color solutions of film forming polymers in yellow to orange shades.
German Patent Publication DE 3538517 and U.S. Pat. No. 5,037,964 (Moser et al.), the disclosures of each of which are totally incorporated herein by reference, disclose sulfonic acid group-free basic azo compounds, which correspond in one of the possible tautomeric forms to the formula 
their preparation and their use for dyeing paper.
Japanese Patent Publication JP 03192158, the disclosure of which is totally incorporated herein by reference, discloses obtaining a yellow dye exhibiting high dyeing speed and degree of exhaustion in dyeing a textile material, leather, pulp, paper, etc., as well as excellent brightness and fastness to water by selecting a compound wherein a pyridopyridinium salt is linked to diphenylfluorene through azo groups. A cationic compound of the formula 
wherein R1 is H or 1-4C alkyl; R2 is H, 1-4C alkyl, or alkoxy; and Axe2x88x92 is an anion which has a structure wherein a tetrazo compound, of 9,9xe2x80x2-bis(4-anilino) fluorene is coupled with a pyridone derivative yellow dye, which is useful for dyeing an unsized pulp or paper (e.g. a napkin, table cloth, or sanitary paper). The dyeing with the dye is carried out at a pH of 4-8, preferably 5-7, and at 10-50xc2x0 C., preferably 15-30xc2x0 C.
British Patent Publication GB 2 008 606, the disclosure of which is totally incorporated herein by reference, discloses water-insoluble yellow monoazo dyes suitable for dyeing hydrophobic synthetic fibres, particularly polyesters, having the formula 
in which X represents OR3 or NHR3, NR3R4 (R3, R4 together optionally forming with N a ring having 5 to 6 carbon atoms, NHR5; R1 represents a hydrogen atom, an alkyl having 1 to 5 carbon atoms, (CH2)2OH or (CH2)3OR3; R2 represents CN, COOR3, CONHR3, CONR3R4 (R3, R4 together optionally forming with N a ring having 5 to 6 carbon atoms); R3 and R4 represent alkyl groups having 1 to 5 carbon atoms; and R5 represents a cycloalkyl having 5 or 6 carbon atoms. The dyes may be prepared by the reaction of 
with Hal-CH2 xe2x80x94COxe2x80x94X in which Hal represents Cl or Br.
xe2x80x9cPreparation and Evaluation of Yellow Pigments Based on H-Pyridone and Esters of Aminoterephthalic Acid,xe2x80x9d P. Slosar et al., CHEMagazin, Vol. 9, No. 6, pp. 8-11 (1999), the disclosure of which is totally incorporated herein by reference, discloses yellow pigments based on H-pyridone and esters of aminoterephthalic acid wherein the color strength, brilliance (purity), and deepening of greenish shade were the larger the smaller alkyl is in the carbalkoxy group in o-position towards the azo group and the greater alkyl is in the carbalkoxy group in m-position towards the azo group.
Of potential background interest with respect to the present invention are the following references: U.S. Pat. No. 5,919,839; U.S. Pat. No. 5,827,918; U.S. Pat. No. 4,889,560; U.S. Pat. No. 5,372,852; xe2x80x9cSynthesis, Morphology, and Optical Properties of Tetrahedral Oligo(phenylenevinylene) Materials,xe2x80x9d S. Wang et al., J. Am. Chem. Soc., Vol. 120, p. 5695 (2000); xe2x80x9cSyntheses of Amphiphilic Diblock Copolymers Containing a Conjugated Block and Their Self-Assembling Properties,xe2x80x9d H. Wang et al., J. Am. Chem. Soc., Vol. 122, p. 6855 (2000); xe2x80x9cCrystal Engineering of Conjugated Oligomers and the Spectral Signature of xcfx80 Stacking in Conjugated Oligomers and Polymers,xe2x80x9d A. Koren et al., Chem. Mater., Vol. 12, p. 1519 (2000); xe2x80x9cInvestigation of the Reaction Conditions for the Synthesis of 4,6-Disubstituted-3-cyano-2-pyridones and 4-Methyl-3-cyano-6-hydroxy-2-pyridone,xe2x80x9d D. Z. Mijin et al., J. Serb. Chem. Soc., Vol. 59, No. 12, p. 959 (1994); xe2x80x9cSynthesis of Isoquinoline Alkaloids. II. The Synthesis and Reactions of 4-Methyl-3-pyridinecarboxaldehyde and Other 4-Methyl-3-substituted Pyridines, J. M. Bobbitt et al., J. Org. Chem., Vol 25, p. 560 (1960); xe2x80x9cSynthesis and Dyeing Characteristics of 5-(4-Arylazophenyl) azo-3-cyano-4-methyl-6-hydroxy-2-pyridones,xe2x80x9d J. Kanhere et al., Indian Journal of Textile Research, Vol. 13, p. 213 (1988); xe2x80x9cSynthesis of Some Pyridone Azo Dyes from 1 Substituted 2-Hydroxy-6-pyridone Derivatives and their Colour Assessment,xe2x80x9d C. Chen et al., Dyes and Pigments, Vol. 15, p. 69- (1991); German Patent Publication DE 3543360; Japanese Patent Publication JP 2001214083; German Patent Publication DE 3505899; Indian Patent Publication 147527; European Patent Publication EP 0 524 637; European Patent Publication EP 0 529 282; European Patent Publication EP 0 083 553; Japanese Patent Publication JP 2000 62327; Japanese Patent Publication JP 85152563; xe2x80x9cSynthesis of 3 Cyano-6-hydroxy-5-( 2-(perfluoroalkyl)phenylazo)-2-pyridones and their Application for Dye Diffusion Thermal Transfer Printing,xe2x80x9d Bull. Chem. Soc. Jpn., 1993, Vol. 66, Iss. 6, Pp.1790-4; European Patent Publication 0 844 287; European Patent Publication 0 404 493; U.S. Pat. No. 5,902,841, U.S. Pat. No. 5,621,022; U.S. Pat. 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No. 4,734,349; Japanese Patent Publication JP 87290762 (JP62290762); Japanese Patent Publication JP 86244595 (JP61244595); Indian Patent Publication IN 147868; Spanish Patent Publication 475254 (Equivalent of Italian Patent Publication IT 1088895); German Patent Publication DE 2727809; xe2x80x9cColour and Constitution of Azo Dyes Derived from 2-Thioalkyl-4,6-Diaminopyrimidines and 3 Cyano-1,4-dimethyl-6-hydroxy-2Coupling Components,xe2x80x9d L. Cheng et al., Dyes and Pigments, Vol. 7, No. 5, pp. 373-388 (1986); European Patent Publication 1 168 046; U.S. Pat. No. 4,644,058; Japanese Patent Publication JP 63039380; Japanese Patent Publication JP 54102328, Japanese Patent Publication JP 54070337; xe2x80x9cTrends in Modern Dye Chemistry. Part 10,xe2x80x9d N. R. Ayyangar and K. V. Srinivasan, Colourage, Vol. 37, No. 2, pp. 29-30 (Jan. 16, 1990); European Patent Publication EP 0 172 283; Japanese Patent Publication JP 05169854; Japanese Patent Publication JP 04292988; Japanese Patent Publication JP 63161060; Japanese Patent Publication JP 61244595; Korean Patent Publication KR 119563; European Patent Publication EP 0 142 863; European Patent Publication EP 0 023 770; Japanese Patent Publication JP 00239549 (JP2000239549); Japanese Patent Publication JP 11269402; Japanese Patent Publication JP 09041267; Japanese Patent Publication JP 08039941; U.S. Pat. No. 4,994,564; Japanese Patent Publication JP 06294909; Japanese Patent Publication JP 06122829; Japanese Patent Publication JP 05255602; Japanese Patent Publication JP 05051536; Japanese Patent Publication JP 04235093; European Patent Publication EP 0 468 647; European Patent Publication EP 0063275; U.S. Pat. No. 4,216,145; and German Patent Publication DE 2606506; the disclosures of each of which are totally incorporated herein by reference.
While known compositions and processes are suitable for their intended purposes, a need remains for improved methods for preparing dianthranilate compounds. In addition, a need remains for methods for preparing dianthranilate compounds containing relatively large hydrocarbon moieties. Further, a need remains for methods for preparing dianthranilate compounds containing relatively large hydrocarbon moieties that enable desirably high product yields. Additionally, a need remains for methods for preparing dianthranilate compounds containing relatively large hydrocarbon moieties that enable desirably high degrees of conversion of reactants to products. There is also a need for methods for preparing dianthranilate compounds containing relatively large hydrocarbon moieties that are environmentally safe. In addition, there is a need for methods for preparing dianthranilate compounds containing relatively large hydrocarbon moieties that are cost-effective. Further, there is a need for methods for preparing dianthranilate compounds containing relatively large hydrocarbon moieties that employ readily available starting materials. Additionally, there is a need for methods for preparing dianthranilate compounds containing relatively large hydrocarbon moieties that entail desirably simple processes. A need also remains for methods for preparing dianthranilate compounds containing relatively large hydrocarbon moieties that require desirably short periods of time. In addition, a need remains for methods for preparing dianthranilate compounds containing relatively large hydrocarbon moieties that afford dianthranilates uncontaminated with any monoanthranilate-mono alcohol (that otherwise might have been formed as an intermediate during the synthesis). Further, a need remains for methods for preparing dianthranilate compounds containing relatively large hydrocarbon moieties that afford the product in relatively high purity without the need for post-synthetic treatments such as recrystallization, distillation, or column chromatography. Additionally, a need remains for methods for preparing diazopyridone colorants that have the aforementioned advantages.
The present invention is directed to a process for preparing dianthranilate compounds which comprises (a) admixing (1) a diol of the formula R1(OH)2, wherein R1 is an alkylene group having at least about 20 carbon atoms, and wherein the xe2x80x94OH groups are primary or secondary, (2) isatoic anhydride, present in an amount of at least about 2 moles of isatoic anhydride per every one mole of diol, (3) a catalyst which is 1,4-diazabicyclo[2.2.2]octane, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylethylene diamine, or a mixture thereof, said catalyst being present in an amount of at least about 0.2 mole of catalyst per every one mole of diol, and (4) a solvent; and (b) heating the mixture thus formed to form a dianthranilate compound of the formula 
Another embodiment of the present invention is directed to a process for preparing a diazopyridone colorant which comprises (I) preparing a dianthranilate compound by (a) admixing (1) a diol of the formula R1(OH)2, wherein R1 is an alkylene group having at least about 20 carbon atoms, and wherein the xe2x80x94OH groups are primary or secondary, (2) isatoic anhydride, present in an amount of at least about 2 moles of isatoic anhydride per every one mole of diol, (3) a catalyst which is 1,4-diazabicyclo [2.2.2]octane, N,N,Nxe2x80x2, Nxe2x80x2-tetramethylethylene diamine, or a mixture thereof, said catalyst being present in an amount of at feast about 0.2 mole of catalyst per every one mole of diol, and (4) a solvent; and (b) heating the mixture thus formed to form a dianthranilate compound of the formula 
(II) reacting the dianthranilate compound with nitrosylsulfuric acid to form a diazonium salt of the formula 
and (III) reacting the diazonium salt with a pyridone compound of the formula 
wherein R2 is (i) an alkyl group, (ii) an aryl group, (iii) an arylalkyl group, (iv) an alkylaryl group, (v) an alkoxy group, (vi) an aryloxy group, (vii) an arylalkyloxy group, (viii) an alkylaryloxy group, (ix) a polyalkyleneoxy group, (x) a polyaryleneoxy group, (xi) a polyarylalkyleneoxy group, (xii) a polyalkylaryleneoxy group, (xiii) a heterocyclic group, (xiv) a silyl group, (xv) a siloxane group, (xvi) a polysilylene group, (xvii) a polysiloxane group, or (xviii) a group of the formula 
wherein r and s are each, independently of the other, integers representing a number of repeat xe2x80x94CH2xe2x80x94 groups, and R3 is (i) an alkyl group, (ii) an aryl group, (iii) an arylalkyl group, or (iv) an alkylaryl. group, to form a diazopyridone compound of the formula 
Dianthranilate compounds are prepared according to the present invention by reacting isatoic anhydride with the selected diol in the presence of a base catalyst and a solvent and heating to form the desired product, as follows: 
The selected diol is one wherein the hydroxy groups are either primary (i.e., connected to a carbon atom which is connected to one other carbon atom) or secondary (i.e., connected to a carbon atom which is connected to two other carbon atoms). In the diol of formula R1(OH)2, R1 is an alkylene group (including linear, branched, saturated, unsaturated, and cyclic alkylene groups), in one embodiment with at least about 20 carbon atoms, in another embodiment with at least about 22 carbon atoms, in still another embodiment with at least about 24 carbon atoms, in another embodiment with at least about 26 carbon atoms, in yet another embodiment with at least about 28 carbon atoms, in still another embodiment with at least about 30 carbon atoms, in another embodiment with at least about 32 carbon atoms, in yet another embodiment with at least about 34 carbon atoms, and in still another embodiment with at least about 36 carbon atoms, and in one embodiment with no more than about 200 carbon atoms, in another embodiment with no more than about 100 carbon atoms, in yet another embodiment with no more than about 75 carbon atoms, in still another embodiment with no more than about 60 carbon atoms, in another embodiment with no more than about 50 carbon atoms, and in yet another embodiment with no more than about 40 carbon atoms, although the number of carbon atoms can be outside of these ranges. In a specific embodiment, R1 is a branched alkyl group of the formula xe2x80x94C36H64+nxe2x88x92 wherein n is an integer of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, which may include unsaturations and cyclic groups. One specific example of R1 is a group of the formula 
Examples of suitable R1(OH)2 compounds include a branched C36 dimer diol commercially available from Uniqema (New Castle, Del.) under the trade name PRIPOL(copyright) 2033, including isomers of the formula 
and other branched isomers (which may include unsaturations and cyclic groups) (further information on C36 dimer diols of this type is disclosed in, for example, xe2x80x9cDimer Acids,xe2x80x9d Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 8, 4th Ed. (1992), pp. 223 to 237, the disclosure of which is totally incorporated herein by reference) and the like.
Isatoic anhydride and the selected diol are present in any desired or effective relative amounts, in one embodiment at least about 2 moles of isatoic anhydride per every one mole of diol, in another embodiment at least about 2.05 moles of isatoic anhydride per every one mole of diol, in yet another embodiment at least about 2.1 moles of isatoic anhydride per every one mole of diol, and in still another embodiment at least about 2.2 moles of isatoic anhydride per every one mole of diol, and in one embodiment no more than about 5 moles of isatoic anhydride per every one mole of diol, in another embodiment no more than about 3 moles of isatoic anhydride per every one mole of diol, and in yet another embodiment no more than about 2.5 moles of isatoic anhydride per every one mole of diol, although the relative amounts of reactants can be outside of these ranges.
The catalyst is 1,4-diazabicyclo[2.2.2]octane, N,N,Nxe2x80x2, Nxe2x80x2-tetramethylethylene diamine, or a mixture thereof. The catalyst is present in the reaction mixture in any desired or effective amount, in one embodiment at least about 0.2 mole of catalyst per every one mole of diol, in another embodiment at least about 0.22 mole of catalyst per every one mole of diol, in yet another embodiment at least about 0.25 mole of catalyst per every one mole of diol, and in still another embodiment at least about 0.5 mole of catalyst per every one mole of diol, and in one embodiment no more than about 2 moles of catalyst per every one mole of diol, in another embodiment no more than about 1 mole of catalyst per every one mole of diol, and in yet another embodiment no more than about 0.5 mole of catalyst per every one mole of diol, although the relative amount of catalyst can be outside of these ranges.
The reactants typically are present in a suitable solvent. The reactants can be either soluble or insoluble in the solvent, resulting in a homogeneous or a heterogeneous reaction mixture. Examples of suitable solvents include toluene, xylene, methyl ethyl ketone, ethyl acetate, butyl acetate, chlorobenzene, dioxane, dimethylformamide, N-methyl-2-pyrrolidinone, dimethylsulfoxide, sulfolane, pyridone, and the like, as well as mixtures thereof, with toluene and butyl acetate being preferred.
The reactants can be present in the solvent in any desired or effective relative amounts. The solvent is present in an amount of in one embodiment at least about 0.1 mole of diol per liter of solvent, in another embodiment at least about 0.25 mole of diol per liter of solvent, in yet another embodiment at least about 0.5 mole of diol per liter of solvent, and in still another embodiment at least about 0.75 mole of diol per liter of solvent, and is present in an amount of in one embodiment no more than about 3 moles of diol per liter of solvent, in another embodiment no more than about 2 moles of diol per liter of solvent, in yet another embodiment no more than about 1.5 moles of diol per liter of solvent , and in still another embodiment no more than about 0.75 mole of diol per liter of solvent, although the relative amount of solvent can be outside of these ranges.
The reaction mixture is heated to any desired or effective temperature, in one embodiment to a temperature of at least about 40xc2x0 C., in another embodiment to a temperature of at least about 75xc2x0 C., and in yet another embodiment to a temperature of at least about 100xc2x0 C., and is heated in one embodiment to a temperature of no more than about 200xc2x0 C. in another embodiment to a temperature of no more than about 170xc2x0 C., and in yet another embodiment of no more than about 150xc2x0 C., although the temperature can be outside of these ranges.
The reaction is carried out by heating for any desired or effective amount of time, in one embodiment for a period of at least about 1 hour, in another embodiment for a period of at least about 2.5 hours, and in yet another embodiment for a period of at least about 3 hours, and in one embodiment for a period of no more than about 10 hours, in another embodiment for a period of no more than about 6 hours, and in yet another embodiment for a period of no more than about 3.5 hours, although the reaction time can be outside of these ranges.
Subsequent to completion of the reaction, excess isatoic anhydride can be quenched, by, for example, the dropwise addition of a dilute solution (about 5 percent, for example) of aqueous sodium or potassium hydroxide to convert isatoic anhydride to the water-soluble sodium or potassium salt of anthranilic acid. Alternately, excess isatoic anhydride can be reacted with methanol or ethanol, which converts it to methyl or ethyl anthranilate, both of which are liquids soluble in common organic solvents, such as alcohols, ethers, ketones, esters, and the like.
The dianthranilate product can be separated from the reaction mixture by any desired or effective method. For example, liquid-liquid extraction, which may be desirable when the dianthranilate is not crystalline at ambient temperature, can be carried out between the organic phase and the aqueous phase of the mixture. (Said aqueous phase can be added when the reaction mixture is subjected to quenching with an aqueous solution; when such quenching is not carried out, water can be added to create the aqueous phase.) In the event of formation of an emulsion between these phases, which could make separation of the layers difficult or very slow, techniques known to those skilled in the art of extractive separation, such as, for example, adding more of the same or a different organic solvent to the organic layer, such as ethyl acetate or the like, and/or adding a salt, such as, for example, sodium chloride, potassium chloride, ammonium sulfate, or the like (typically in amounts from about 5 to about 30 percent by weight in water) can be performed. The organic phase can then, if desired, be dried by any desired or effective method, such as by drying over magnesium sulfate, or the like. The product can then be isolated by removal of the solvent by any desired or effective method, such as vacuum distillation or the like. If desired, the resulting product, while it is still dissolved in the organic phase, can be treated with acidic media, such as an acid-leached bentonite clay (available from Englehart Industries under the Trade name FILTROL(copyright) 24), which treatment can serve to remove any undesirable colored basic impurities.
The dianthranilate product can also be separated from the reaction mixture by precipitation using a non-solvent, which may be desirable when the dianthranilate product is crystalline. In this situation, a low alcohol, such as methanol or ethanol, is added to the reaction mixture in a molar amount greater than or equal to the amount of unreacted isatoic anhydride, either after cooling to room temperature or at a temperature of up to about 80xc2x0 C., which serves to convert excess isatoic anhydride to the liquid methyl or ethyl anthranilate. Addition of a non-solvent for the dianthranilate, such as water, methanol, isopropanol, or the like is then used to precipitate the product, which can then be separated by filtration, washing with a suitable solvent, and drying.
The dianthranilate compounds prepared according to the present invention can be used as intermediates in the preparation of diazopyridone colorant molecules. The pyridones with which the dianthranilate compounds are reacted are of the general formula 
wherein R2 is (i) an alkyl group (including linear, branched, saturated, unsaturated, cyclic, unsubstituted, and substituted alkyl groups, and wherein hetero atoms, such as oxygen, nitrogen, sulfur, silicon, phosphorus, and the like either may or may not be present in the alkyl group), in one embodiment with at least 1 carbon atom, in another embodiment with at least about 8 carbon atoms, in yet another embodiment with at least about 10 carbon atoms, in still another embodiment with at least about 12 carbon atoms, in another embodiment with at least about 14 carbon atoms, in yet another embodiment with at least about 16 carbon atoms, in still another embodiment with at least about 18 carbon atoms, in another embodiment with at least about 20 carbon atoms, in yet another embodiment with at least about 22 carbon atoms, in still another embodiment with at least about 24 carbon atoms, in another embodiment with at least about 26 carbon atoms, in yet another embodiment with at least about 28 carbon atoms, in still another embodiment with at least about 30 carbon atoms, in another embodiment with at least about 32 carbon atoms, in yet another embodiment with at least about 34 carbon atoms, and in still another embodiment with at least about 36 carbon atoms, and in one embodiment with no more than about 200 carbon atoms, in another embodiment with no more than about 100 carbon atoms, in yet another embodiment with no more than about 75 carbon atoms, in still another embodiment with no more than about 60 carbon atoms, in another embodiment with no more than about 50 carbon atoms, and in yet another embodiment with no more than about 40 carbon atoms, although the number of carbon atoms can be outside of these ranges, (ii) an aryl group (including unsubstituted and substituted aryl groups), in one embodiment with at least about 6 carbon atoms, in another embodiment with at least about 10 carbon atoms, in yet another embodiment with at least about 13 carbon atoms, in still another embodiment with at least about 14 carbon atoms, in another embodiment with at least about 16 carbon atoms, in yet another embodiment with at least about 17 carbon atoms, in still another embodiment with at least about 18 carbon atoms, in another embodiment with at least about 19 carbon atoms, in yet another embodiment with at least about 20 carbon atoms, in still another embodiment with at least about 21 carbon atoms, in another embodiment with at least about 22 carbon atoms, and in yet another embodiment with at least about 23 carbon atoms, and in one embodiment with no more than about 100 carbon atoms, in another embodiment with no more than about 75 carbon atoms, and in yet another embodiment with no more than about 50 carbon atoms, although the number of carbon atoms can be outside of these ranges, (iii) an arylalkyl group (including unsubstituted and substituted arylalkyl groups), in one embodiment with at least about 7 carbon atoms, in another embodiment with at least about 8 carbon atoms, in another embodiment with at least about 10 carbon atoms, in yet another embodiment with at least about 12 carbon atoms, in still another embodiment with at least about 14 carbon atoms, in another embodiment with at least about 16 carbon atoms, in yet another embodiment with at least about 18 carbon atoms, in still another embodiment with at least about 20 carbon atoms, in another embodiment with at least about 22 carbon atoms, in yet another embodiment with at least about 24 carbon atoms, in still another embodiment with at least about 26 carbon atoms, in another embodiment with at least about 28 carbon atoms, in yet another embodiment with at least about 30 carbon atoms, in still another embodiment with at least about 32 carbon atoms, in another embodiment with at least about 34 carbon atoms, in yet another embodiment with at least about 36 carbon atoms, in another embodiment with at least about 38 carbon atoms, in yet another embodiment with at least about 40 carbon atoms, and in still another embodiment with at least about 42 carbon atoms, and in one embodiment with no more than about 200 carbon atoms, in another embodiment with no more than about 100 carbon atoms, and in yet another embodiment with no more than about 44 carbon atoms, although the number of carbon atoms can be outside of these ranges, (iv) an alkylaryl group (including unsubstituted and substituted alkylaryl groups), in one embodiment with at least about 7 carbon atoms, in another embodiment with at least about 8 carbon atoms, in another embodiment with at least about 10 carbon atoms, in yet another embodiment with at least about 12 carbon atoms, in still another embodiment with at least about 14 carbon atoms, in another embodiment with at least about 16 carbon atoms, in yet another embodiment with at least about 18 carbon atoms, in still another embodiment with at least about 20 carbon atoms, in another embodiment with at least about 22 carbon atoms, in yet another embodiment with at least about 24 carbon atoms, in still another embodiment with at least about 26 carbon atoms, in another embodiment with at least about 28 carbon atoms, in yet another embodiment with at least about 30 carbon atoms, in still another embodiment with at least about 32 carbon atoms, in another embodiment with at least about 34 carbon atoms, in yet another embodiment with at least about 36 carbon atoms, in another embodiment with at least about 38 carbon atoms, in yet another embodiment with at least about 40 carbon atoms, and in still another embodiment with at least about 42 carbon atoms, and in one embodiment with no more than about 200 carbon atoms, in another embodiment with no more than about 100 carbon atoms, and in yet another embodiment with no more than about 44 carbon atoms , although the number of carbon atoms can be outside of these ranges, (v) an alkoxy group (including linear, branched, saturated, unsaturated, cyclic, unsubstituted, and substituted alkoxy groups, and wherein hetero atoms, such as oxygen, nitrogen, sulfur, silicon, phosphorus, and the like either may or may not be present in the alkyl portion of the alkoxy group), in one embodiment with at least 1 carbon atom, in another embodiment with at least about 8 carbon atoms, in yet another embodiment with at least about 10 carbon atoms, in still another embodiment with at least about 12 carbon atoms, in another embodiment with at least about 14 carbon atoms, in yet another embodiment with at least about 16 carbon atoms, in still another embodiment with at least about 18 carbon atoms, in another embodiment with at least about 20 carbon atoms, in yet another embodiment with at least about 22 carbon atoms, in still another embodiment with at least about 24 carbon atoms, in another embodiment with at least about 26 carbon atoms, in yet another embodiment with at least about 28 carbon atoms, in still another embodiment with at least about 30 carbon atoms, in another embodiment with at least about 32 carbon atoms, in yet another embodiment with at least about 34 carbon atoms, and in still another embodiment with at least about 36 carbon atoms, and in one embodiment with no more than about 200 carbon atoms, in another embodiment with no more than about 100 carbon atoms, in yet another embodiment with no more than about 75 carbon atoms, in still another embodiment with no more than about 60 carbon atoms, in another embodiment with no more than about 50 carbon atoms, and in yet another embodiment with no more than about 40 carbon atoms, although the number of carbon atoms can be outside of these ranges, (vi) an aryloxy group (including unsubstituted and substituted aryloxy groups), in one embodiment with at least about 6 carbon atoms, in another embodiment with at least about 10 carbon atoms, in yet another embodiment with at least about 13 carbon atoms, in still another embodiment with at least about 14 carbon atoms, in another embodiment with at least about 16 carbon atoms, in yet another embodiment with at least about 17 carbon atoms, in still another embodiment with at least about 18 carbon atoms, in another embodiment with at least about 19 carbon atoms, in yet another embodiment with at least about 20 carbon atoms, in still another embodiment with at least about 21 carbon atoms, in another embodiment with at least about 22 carbon atoms, and in yet another embodiment with at least about 23 carbon atoms, and in one embodiment with no more than about 100 carbon atoms, in another embodiment with no more than about 75 carbon atoms, and in yet another embodiment with no more than about 50 carbon atoms, although the number of carbon atoms can be outside of these ranges, (vii) an arylalkyloxy group (including unsubstituted and substituted arylalkyloxy groups), in one embodiment with at least about 7 carbon atoms, in another embodiment with at least about 8 carbon atoms, in another embodiment with at least about 10 carbon atoms, in yet another embodiment with at least about 12 carbon atoms, in still another embodiment with at least about 14 carbon atoms, in another embodiment with at least about 16 carbon atoms, in yet another embodiment with at least about 18 carbon atoms, in still another embodiment with at least about 20 carbon atoms, in another embodiment with at least about 22 carbon atoms, in yet another embodiment with at least about 24 carbon atoms, in still another embodiment with at least about 26 carbon atoms, in another embodiment with at least about 28 carbon atoms, in yet another embodiment with at least about 30 carbon atoms, in still another embodiment with at least about 32 carbon atoms, in another embodiment with at least about 34 carbon atoms, in yet another embodiment, with at least about 36 carbon atoms, in another embodiment with at least about 38 carbon atoms, in yet another embodiment with at least about 40 carbon atoms, and in still another embodiment with at least about 42 carbon atoms, and in one embodiment with no more than about 200 carbon atoms, in another embodiment with no more than about 100 carbon atoms, and in yet another embodiment with no more than about 44 carbon atoms, although the number of carbon atoms can be outside of these ranges, (viii) an alkylaryloxy group (including unsubstituted and substituted alkylaryloxy groups), in one embodiment with at least about 7 carbon atoms, in another embodiment with at least about 8 carbon atoms, in another embodiment with at least about 10 carbon atoms, in yet another embodiment with at least about 12 carbon atoms, in still another embodiment with at least about 14 carbon atoms, in another embodiment with at least about 16 carbon atoms, in yet another embodiment with at least about 18 carbon atoms, in still another embodiment with at least about 20 carbon atoms, in another embodiment with at least about 22 carbon atoms, in yet another embodiment with at least about 24 carbon atoms, in still another embodiment with at least about 26 carbon atoms, in another embodiment with at least about 28 carbon atoms, in yet another embodiment with at least about 30 carbon atoms, in still another embodiment with at least about 32 carbon atoms, in another embodiment with at least about 34 carbon atoms, in yet another embodiment with at least about 36 carbon atoms, in another embodiment with at least about 38 carbon atoms, in yet another embodiment with at least about 40 carbon atoms, and in still another embodiment with at least about 42 carbon atoms, and in one embodiment with no more than about 200 carbon atoms, in another embodiment with no more than about 100 carbon atoms, and in yet another embodiment with no more than about 44 carbon atoms, although the number of carbon atoms can be outside of these ranges, (ix) a polyalkyleneoxy group, wherein the alkyl portion of the repeat alkyleneoxy groups typically has from about 1 to about 12 carbon atoms, although the number of carbon atoms can be outside of these ranges, such as a polyethyleneoxy group, a polypropyleneoxy group, a polybutyleneoxy group, or the like, and wherein the number of repeat alkyleneoxy groups typically is from about 2 to about 50 repeat alkyleneoxy groups, although the number of repeat units can be outside of these ranges, (x) a polyaryleneoxy group, wherein the aryl portion of the repeat aryleneoxy groups typically has from about 6 to about 14 carbon atoms, although the number of carbon atoms can be outside of these ranges, such as a polyphenyleneoxy group, a polynaphthaleneoxy group, a polyphenanthreneoxy group, or the like, and wherein the number of repeat aryleneoxy groups typically is from about 2 to about 20 repeat aryleneoxy groups, although the number of repeat units can be outside of these ranges, (xi) a polyarylalkyleneoxy group, wherein the arylalkyl portion of the repeat arylalkyleneoxy groups typically has from about 7 to about 50 carbon atoms, although the number of carbon atoms can be outside of these ranges, such as a polybenzyleneoxy group, a polyphenylethyleneoxy group, or the like, and wherein the number of repeat arylalkyleneoxy groups typically is from about 2 to about 20 repeat arylalkyleneoxy groups, although the number of repeat units can be outside of these ranges, (xii) a polyalkylaryleneoxy group, wherein the alkylaryl portion of the repeat alkylaryleneoxy groups typically has from about 7 to about 50 carbon atoms, although the number of carbon atoms can be outside of these ranges, such as a polytolueneoxy group or the like, and wherein the number of repeat alkylaryleneoxy groups typically is from about 2 to about 20 repeat alkylaryleneoxy groups, although the number of repeat units can be outside of these ranges, (xiii) a heterocyclic group (including unsubstituted and substituted heterocyclic groups), typically with from about 2 to about 12 carbon atoms, and typically with from about 4 to about 18 ring atoms, although the number of carbon atoms and the number of ring atoms can be outside of these ranges, wherein the heteroatoms in the heterocyclic groups can be (but are not limited to) nitrogen, oxygen, sulfur, silicon, phosphorus, and the like, as well as mixtures thereof, (xiv) a silyl group (including unsubstituted and substituted silyl groups), (xv) a siloxane group (including unsubstituted and substituted siloxane groups), (xvi) a polysilylene group (including unsubstituted and substituted polysilylene groups), typically with from 2 to about 100 repeat silylene units, (xvii) a polysiloxane group (including unsubstituted and substituted polysiloxane groups), typically with from 2 to about 200 repeat siloxane units, although the number of repeat siloxane units can be outside of this range, or (xviii) a group of the formula 
wherein r is an integer representing the number of repeat xe2x80x94CH2xe2x80x94 groups, in one embodiment being at least 1, in another embodiment at least about 5, and in yet another embodiment at least about 10, and in one embodiment being no more than about 100, in another embodiment no more than about 50, and in yet another embodiment no more than about 25, although the value of r can be outside of these ranges, and wherein s is an integer representing the number of repeating xe2x80x94CH2xe2x80x94 groups, in one embodiment being at least 1, in another embodiment at least about 5, and in yet another embodiment at least about 10, and in one embodiment being no more than about 100, in another embodiment no more than about 50, and in yet another embodiment no more than about 25, although the value of s can be outside of these ranges, wherein the substituents on the substituted alkyl, aryl, arylalkyl, alkylaryl, alkoxy, aryloxy, arylalkyloxy, alkylaryloxy, polyalkyleneoxy, polyaryleneoxy, polyarylalkyleneoxy, polyalkylaryleneoxy, heterocyclic, silyl, siloxy, polysilylene, and polysiloxy groups are hydroxy groups, halogen atoms, cyano groups, ether groups, aldehyde groups, ketone groups, carboxylic acid groups, ester groups, amide groups, carbonyl groups, thiocarbonyl groups, sulfate groups, sulfonate groups, sulfide groups, sulfoxide groups, phosphate groups, nitrile groups, mercapto groups, nitro groups, nitroso groups, sulfone groups, acyl groups, acid anhydride groups, azide groups, cyanato groups, isocyanato groups, thiocyanato groups, isothiocyanato groups, mixtures thereof, and the like, wherein the substituents on the silylene, siloxy, polysilylene, and polysiloxy groups can also be alkyl groups, aryl groups, arylalkyl groups, and alkylaryl groups, wherein two or more substituents can be joined together to form a ring.
Some specific examples of suitable R2 groups include (but are not limited to) ethyl, of the formula xe2x80x94CH2CH3, n-butyl, of the formula xe2x80x94(CH2)3CH3, n-octyl, of the formula xe2x80x94(CH2)7CH3, n-decyl, of the formula xe2x80x94(CH2)9CH3, n-dodecyl, of the formula xe2x80x94(CH2)11CH3, n-tetradecyl, of the formula xe2x80x94(CH2)13CH3, cetyl, of the formula xe2x80x94(CH2)15CH3, stearyl, of the formula xe2x80x94(CH2)17CH3, 2-ethylhexyl, of the formula 
abietyl, including groups of the formula 
as well as hydrogenated and dehydrogenated isomers of the above formula that are also derivatives of the rosin-derived natural product abietic acid, such as didehydroabietyl and the like, 3-propyl octadecanoyl, of the formula 
2,2-dimethyl-1,3-dioxolane-4-methylene, of the formula 
and the like.
R3 is (i) an alkyl group (including linear, branched, saturated, unsaturated, cyclic, unsubstituted, and substituted alkyl groups, and wherein hetero atoms, such as oxygen, nitrogen, sulfur, silicon, phosphorus, and the like can be present in the alkyl group), typically with from 1 to about 100 carbon atoms, preferably with from about 1 to about 10 carbon atoms, and more preferably with from about 1 to about 5 carbon atoms, although the number of carbon atoms can be outside of these ranges, (ii) an aryl group (including unsubstituted and substituted aryl groups), typically with from about 6 to about 100 carbon atoms, and preferably with from about 6 to about 10 carbon atoms, although the number of carbon atoms can be outside of these ranges, (iii) an arylalkyl group (including unsubstituted and substituted arylalkyl groups), typically with from about 7 to about 100 carbon atoms, and preferably with from about 7 to about 10 carbon atoms, although the number of carbon atoms can be outside of these ranges, or (iv) an alkylaryl group (including unsubstituted and substituted alkylaryl groups), typically with from about 7 to about 100 carbon atoms, and preferably with from about 7 to about 10 carbon atoms, although the number of carbon atoms can be outside of these ranges, wherein the substituents on the substituted alkyl, aryl, arylalkyl, and alkylaryl groups can be (but are not limited to) hydroxy groups, halogen atoms, amine groups, imine groups, ammonium groups, pyridine groups, pyridinium groups, ether groups, aldehyde groups, ester groups, amide groups, carbonyl groups, thiocarbonyl groups, sulfate groups, sulfonate groups, sulfide groups, sulfoxide groups, phosphine groups, phosphonium groups, phosphate groups, nitrile groups, mercapto groups, nitro groups, nitroso groups, sulfone groups, acyl groups, acid anhydride groups, azide groups, cyanato groups, isocyanato groups, thiocyanato groups, isothiocyanato groups, mixtures thereof, and the like, wherein two or more substituents can be joined together to form a ring.
Specific examples of suitable R3 groups include methyl (xe2x80x94CH3), linear alkyl groups of the formula xe2x80x94(CH2)cCH3 wherein c is an integer of 1, 2, 3, 4, 5, 6, 7, 8, or 9, and the like.
For example, diazopyridone colorant molecules can be prepared by diazotization of the correspondingly substituted dimeric aniline with nitrosylsulfuric acid under cold temperature conditions, followed by coupling with the correspondingly substituted pyridone in a buffered alkaline aqueous solution under cold temperature conditions, as follows: 
More specifically, the correspondingly substituted dianiline is first subjected to a diazotization reaction by dissolving it in acetic acid diluted with a solvent and, optionally, a second acid, such as sulfuric acid, dodecylbenzene sulfonic acid, propionic acid, hydrochloric acid, phosphoric acid, any other acid useful for a diazotization reaction, or the like, as well as mixtures thereof. The solvent can be any solvent useful in a diazotization reaction, such as water, acetone, dimethylformamide, dimethyacetamide, tetrahydrofuran, dimethoxyethane, analogous higher-boiling ether solvents, and the like, as well as mixtures thereof.
The solvent and the dianiline are present in any desired or effective relative amounts; if, for purposes of determining relative amounts, xe2x80x9csolventxe2x80x9d is defined to include whatever solvent has been selected plus any amount of acetic acid and second acid present, the reactants are present in this combined solvent in relative amounts of in one embodiment at least about 100 grams of substituted dianiline per liter of solvent, in another embodiment at least about 200 grams of substituted dianiline per liter of solvent, and in yet another embodiment at least about 230 grams of substituted dianiline per liter of solvent, and in one embodiment of no more than about 400 grams of substituted dianiline per liter of solvent, in another embodiment of no more than about 300 grams of substituted dianiline per liter of solvent, and in yet another embodiment of no more than about 270 grams of substituted dianiline per liter of solvent, although the relative amounts can be outside of these ranges.
The acetic acid is present in any desired or effective amount, in one embodiment at least about 1 gram of acetic acid per gram of substituted dianiline, in another embodiment at least about 2 grams of acetic acid per gram of substituted dianiline, and in yet another embodiment at least about 3 grams of acetic acid per gram of substituted dianiline, and in one embodiment no more than about 10 grams of acetic acid per gram of substituted dianiline, in another embodiment no more than about 7 grams of acetic acid per gram of substituted dianiline, and in yet another embodiment no more than about 5 grams of acetic acid per gram of substituted dianiline, although the relative amounts can be outside of these ranges.
When present, the optional second acid is present in any desired or effective amount, in one embodiment at least about 0.05 gram of acid per gram of substituted dianiline, and in another embodiment at least about 0.1 gram of acid per gram of substituted dianiline, and in one embodiment no more than about 0.5 grams of acid per gram of substituted dianiline, in another embodiment no more than about 0.3 grams of acid per gram of substituted dianiline, and in yet another embodiment no more than about 0.2 grams of acid per gram of substituted dianiline, although the relative amounts can be outside of these ranges.
In the mixture comprising the selected solvent, any optional second acid, and acetic acid, the acetic acid is present in any desired or effective amount, in one embodiment at least about 50 percent by volume of the mixture, in another embodiment at least about 70 percent by volume of the mixture, in yet another embodiment at least about 75 percent by volume of the mixture, and in still another embodiment at least about 95 percent by volume of the mixture, although the relative amount can be outside of these ranges.
Upon complete dissolution of the ingredients, the mixture is cooled, in one embodiment to a temperature of no more than about +15xc2x0 C., in another embodiment to a temperature of no more than about +10xc2x0 C., in yet another embodiment to a temperature of no more than about +5xc2x0 C., in still another embodiment to a temperature of no more than about +3xc2x0 C., and in one embodiment to a temperature of no lower than about xe2x88x925xc2x0 C., and in another embodiment to a temperature of no lower than about xe2x88x9210xc2x0 C., although the temperature can be outside of these ranges.
Thereafter, nitrosylsulfuric acid is added to the mixture in any desired or effective amount, in one embodiment at least about 2 moles of nitrosylsulfuric acid per mole of substituted dianiline (i.e., at least about 1 mole of nitrosylsulfuric acid per mole of aniline moiety in the dianiline), and in another embodiment at least about 2.1 moles of nitrosylsulfuric acid per mole of substituted dianiline, and in one embodiment no more than about 3 moles of nitrosylsulfuric acid per mole of substituted dianiline, in another embodiment no more than about 2.5 moles of nitrosylsulfuric acid per mole of substituted dianiline, and in yet another embodiment no more than about 2.25 moles of nitrosylsulfuric acid per mole of substituted dianiline, although the relative amounts can be outside of these ranges. In a specific embodiment, the nitrosylsulfuric acid is added dropwise at a rate such that the temperature of the reaction mixture does not exceed 15xc2x0 C.
The reaction to form the diazonium salt is essentially instantaneous, and upon completion of addition of the nitrosylsulfuric acid the reaction is essentially complete, although, if desired, a qualitative test can be performed to confirm reaction completion.
Thereafter, residual excess nitrosylsulfuric acid present in the reaction mixture can be quenched by the addition of a quenching agent, such as sulfamic acid, urea, or the like as well as mixtures thereof, in any desired or effective amount, in one embodiment at least about 0.01 mole of quenching agent per mole of nitrosylsulfuric acid (i.e., per mole of nitrosylsulfuric acid originally added to the reaction mixture), in another embodiment at least about 0.05 mole of quenching agent per mole of nitrosylsulfuric acid, and in yet another embodiment at least about 0.1 mole of quenching agent per mole of nitrosylsulturic acid, and in one embodiment no more than about 0.5 mole of quenching agent per mole of nitrosylsulfuric acid, in another embodiment no more than about 0.3 mole of quenching agent per mole of nitrosylsulfuric acid, and in yet another embodiment no more than about 0.2 mole of quenching agent per mole of nitrosylsulfuric acid, although the amount can be outside of these ranges. Upon completion of the reaction, the reaction mixture contains the corresponding diazonium salt.
A precursor solution of the pyridone having the desired substituents thereon is prepared in an appropriate solvent, such as a mixture of water, organic solvents, including lower alcohols such as methanol, ethanol, isopropanol, and the like, water-miscible nonbasic organic solvents such as tetrahydrofuran, acetone, dimethoxyethane, N,N-dimethylformamide, N,N-dimethylacetamide, and the like, as well as mixtures thereof. Mixtures of water with an organic solvent can be helpful for ease of solvating inorganic or organic salts that are a reaction by-product. In this instance, water and the organic solvent are present in any desired or effective relative amounts, in one embodiment at least about 0.25 gram of organic solvent per gram of water, in another embodiment at least about 0.3 gram of organic solvent per gram of water, and in yet another embodiment at least about 0.4 gram of organic solvent per gram of water, and in one embodiment no more than about 4 grams of organic solvent per gram of water, in another embodiment no more than about 3 grams of organic solvent per gram of water, and in yet another embodiment no more than about 2 grams of organic solvent per gram of water, although the relative amounts can be outside of these ranges.
The pyridone is present in the precursor solution in any desired or effective amount, in one embodiment at least about 10 grams of pyridone per liter of solvent, in another embodiment at least about 30 grams of pyridone per liter of solvent, and in yet another embodiment at least about 50 grams of pyridone per liter of solvent, and in one embodiment no more than about 200 grams of pyridone per liter of solvent, in another embodiment no more than about 100 grams of pyridone per liter of solvent, and in yet another embodiment no more than about 70 grams of pyridone per liter of solvent, although the relative amounts can be outside of these ranges.
The pyridone precursor solution is maintained at an alkaline pH, typically of at least about 10, and in one embodiment no more than about 14, and in another embodiment no more than about 12, although the pH can be outside of these ranges. The pyridone precursor solution can contain a mixture of a base and an optional buffering salt.
Examples of suitable bases include mineral bases, such as sodium hydroxide, potassium hydroxide, and the like, as well as water-miscible organic tertiary amines, such as triethanolamine, N,N-diethylethanolamine, and the like, as well as mixtures thereof, present in any desired or effective amount, in one embodiment at least about 1 mole of base per mole of pyridone, in another embodiment at least about 2 moles of base per mole of pyridone, in yet another embodiment at least about 3 moles of base per mole of pyridone, and in still another embodiment at least about 5 moles of base per mole of pyridone, and in one embodiment no more than about 10 moles of base per mole of pyridone, in another embodiment no more than about 7 moles of base per mole of pyridone, and in yet another embodiment no more than about 5 moles of base per mole of pyridone, although the relative amounts can be outside of these ranges.
Examples of suitable optional buffer salts include those corresponding to the principal acid solvent; for example, when the principal acid solvent is acetic acid, suitable buffers include sodium acetate, potassium acetate, sodium hydrogenphosphate, citric acid, and the like, as well as mixtures thereof. When present, the optional buffer salt is present in any desired or effective amount, in one embodiment at least about 1 mole of buffer per mole of pyridone, in another embodiment at least about 2 moles of buffer per mole of pyridone, in yet another embodiment at least about 3 moles of buffer per mole of pyridone, and in still another embodiment at least about 5 moles of buffer per mole of pyridone, and in one embodiment no more than about 10 moles of buffer per mole of pyridone, in another embodiment no more than about 7 moles of buffer per mole of pyridone, and in yet another embodiment no more than about 5 moles of buffer per mole of pyridone, although the relative amounts can be outside of these ranges. In a specific embodiment, upon dissolution of the pyridone, the thus-formed precursor pyridone solution can be filtered to remove any undissolved solids.
The solution containing the diazonium salt, maintained at a cold temperature, is then slowly added to the pyridone solution in any desired or effective relative amounts, in one embodiment at least about 2 moles of pyridone per mole of diazonium salt, in another embodiment at least about 2.1 moles of pyridone per mole of diazonium salt, and in yet another embodiment at least about 2.25 moles of pyridone per mole of diazonium salt, and in one embodiment no more than about 4 moles of pyridone per mole of diazonium salt, in another embodiment no more than about 3 moles of pyridone per mole of diazonium salt, and in yet another embodiment no more than about 2.5 moles of pyridone per mole of diazonium salt, although the relative amounts can be outside of these ranges, resulting in the immediate formation of a bright yellow precipitate. Thereafter, the yellow precipitate can be collected by filtration and, if desired, washed.
Precursor pyridones can be prepared by any desired or effective method, such as that disclosed in, for example, xe2x80x9cInvestigation of the Reaction Conditions for the Synthesis of 4,6-Disubstituted-3-cyano-2-pyridones and 4-Methyl-3-cyano-6-hydroxy-2-pyridone,xe2x80x9d D. Z. Mijin et al., J. Serb. Chem. Soc., Vol. 59, No. 12, p. 959 (1994); xe2x80x9cSynthesis of Isoquinoline Alkaloids. II. The Synthesis and Reactions of 4-Methyl-3-pyridinecarboxaldehyde and Other 4-Methyl-3-substituted Pyridines, J. M. Bobbitt et al., J. Org. Chem., Vol 25, p. 560 (1960); xe2x80x9cSynthesis and Dyeing Characteristics of 5-(4-Arylazophenyl)azo-3-cyano-4-methyl-6-hydroxy-2-pyridones,xe2x80x9d J. M. Kanhere et al., Indian Journal of Textile Research, Vol. 13, p. 213 (1988): xe2x80x9cSynthesis of Some Pyridone Azo Dyes from 1-Substituted 2-Hydroxy-6-pyridone Derivatives and their Colour Assessment,xe2x80x9d C. Chen et al., Dyes and Pigments, Vol. 15, p. 69 (1991); xe2x80x9cSynthesis of 3 Cyano-6-hydroxy-5-(2-(perfluoroalkyl)phenylazo)-2-pyridones and their Application for Dye Diffusion Thermal Transfer Printing,xe2x80x9d M. Matsui et al., Bull. Chem. Soc. Jpn., 1993, Vol. 66, Iss. 6, Pp. 1790-4; xe2x80x9cSynthesis of N-alkylcyanopyridones,xe2x80x9d B. Peng et al., Faming Zhuanli Shenqing Gongkai Shuomingshu (1997), CN 1158845; xe2x80x9cSynthesis of 1-Butyl-3-cyano-4-methyl-6-hydroxypyrid-2-one,xe2x80x9d X. Kong et al., Huaxue Shiji (1998), 20(1), 58-59; xe2x80x9cRegioselective Conversion of 3 Cyano-6-hydroxy-2-pyridones into 3 Cyano-6-amino-2-pyridones,xe2x80x9d A. R. Katritzky et al., J. Heterocycd. Chem. (1995), 32(3), 1007-10; xe2x80x9cThe Synthesis of Some Hetarylazopyridone Dyes and Solvent Effects on their Absorption Spectra,xe2x80x9d N. Ertan et al., Dyes Pigm. (1995), 27(4), 313-20; xe2x80x9cProcess for the Preparation of Pyridone Compounds,xe2x80x9d H. Schmid, Ger. Offen. DE 4314430 (1994); xe2x80x9cTautomerism of 4-Methyl-6-hydroxy-2-pyridone derivatives,xe2x80x9d H. Liu et al., Dalian Ligong Daxue Xuebao (1992), 32(4), 405-11; xe2x80x9cPreparation of 1-Alkyl-3-cyano-4-methyl-6-hydroxy-2-pyridone-type Mixed Azo Coupling Components,xe2x80x9d J. Prikryl et al., Czech. (1991) 8 pp. CODEN: CZXXA9 CS 273045 B1 19911220 CAN 118:256604 AN 1993:256604 CAPLUS; xe2x80x9cStructural Characteristics of Hydroxypyridone Derivatives,xe2x80x9d Q. Peng et al., Dalian Ligong Daxue Xuebao (1991), 31(3), 279-86; and xe2x80x9c6-Hydroxypyridin-2-ones,xe2x80x9d F. Schmidt, Ger. Offen. DE 2845863 (1980); the disclosures of each of which are totally incorporated herein by reference.